An energy management system (controller) operates on a charging voltage Vba of a specified storage battery out of storage batteries to control power converting operations by bidirectional DC/DC converters. The energy management system controls the power converting operations of the respective bidirectional DC/DC converters so that the SOC of the specified storage battery is always higher than the SOCs of the other storage batteries, executes supplying of power from the other storage batteries to the DC bus with priority over supplying of power from the specified storage battery to the DC bus, and causes the corresponding bidirectional converters to stop the supplying of power from the other storage batteries the DC bus when the SOCs of the storage batteries have fallen below a lower limit value set in advance due to the supplying of power to the DC bus.